Fixed loop antenna mounting



y f F. E. JOHNSTON 2,375,418

FIXED LOOP ANTENNA MOUNTING Filed April 29, 1943 2 Sheets-Sheet 1 Mew).-

QWAMM F. E. JOHNSTON FIXED LOOP ANTENNA MOUNTING 2 sheets sheet 2 FiledApril 29, 1943 May 8, 1945.

t rlillfllllllllfllll' 1 i llfll/IIIAIIIIIIIII!I1O Patented May 8, 1945FIXED LOOP ANTENNA MOUNTING Fred E. Johnston, Evanston, Ill., assignorto Stewart-Warner Corporation, Chicago, 111., a corporation of VirginiaApplication April 29, 1943, Serial No. 484,961

4 Claims.

The invention relates to directional loop antennae and has referencemore particularly to an improved construction for fixedly mounting apair of loops in close association and at right angles with each otherand in a manner to effectively eliminate undesired electric and magneticinfluences.

The primary object of the invention is to provide a mounting for a pairof loop antennae to be used for direction finding purposes which willposition the loops at right angles in relatively close superposedrelation and wherein the electrical conditions surrounding the loopswill provide for eflicient reception with the most accurate directionalindications since all possible sources for disturbances either byinduction or by magnetic influences have been eliminated.

Another object of the present invention resides in the provision of loopantennae of the fixed type which will have particular application to theBellini-Tosi system of radio direction finding. This system uses twostationary loops which heretoiore comprised a large and bulky structureunsuited to present day conditions. The invention contemplates thesubstitution of the improved mounting and loop construction hereindisclosed for the antennae previously employed. The familiar directionalproperties of a loop antenna are utilized in the Bellini-Tosi method ofradio direction finding but since the loops are stationary the angulardisplacement variations are taken care of by a oniometer including amoving search coil which gives the direction of the received radiowaves.

Therefore another object is to provide a mounting for fixed loopantennae which will be compact and highly eflicient, employingrelatively short leads and which are shielded in an improved manner toeliminate distortion of the radio waves before they are picked up by theloops and to also minimize absorption of the energy between loops.

With these and various other objects in view, the invention may consistof certain novel features of construction and operation, as will be morefully described and particularly pointed out 7 in the specification,drawings and claims appended hereto.

In the drawings which illustrate an embodiment of the invention andwherein like reference characters are used to designate like parts--Figure l is an elevational view of the loop mounting of the inventionwith parts of the top 65 e1 p the deck of a ship by a conventionalsupporting means such as indicated in its entirety by numeral it,Figure 1. As illustrated the support comprises the standards H, I 2, l3and I l. The junction box IE contains the necessary sockets 16, ll, l8and 19 for electrically connecting with the leads to the several loops.The external housing 20 of the junction box provides four tubularmembers of non-ferrous material such as brass, and which are angularlyspaced ninety degrees from each other. The members 2| and 22 form thesupport for the top loop 23 and the other members 24 and 25, Figure 2,provide the support for the bottom loop 26. All four members are bent soas to project upwardly and members 2| and 22 additionally include a,vertical portion 28 which extends past the bottom loop 26, beingdisposed on the respective sides thereof. Said members 2i and 22 thuscomprise a yoke and a similar yoke is formed by members 24 and with thejunction box 15 being located centrally of the arrangement.

The top loop 23, as shown in Figure 1, essen tially consists of anelongated iron core 30 of finely divided iron particles having a coil 3|in close association therewith and which coil comprises a large numberof turns of wire extending for substantially the entire length of thecore. A circular form or shell 32 of insulating material is placed overthe iron core and said shell provides the necessary recess for receivingthe windings of the coil 3|. The core and coil combination is suitablyenclosed by a second tubular casing 33 also of insulating material toprotect the windings from the atmosphere. This casing 33 is secured toform 32 by' a plurality of screws 34. The screws additionally secure thecasing to the iron core since they have threaded connection with inserts3'5 of circular shape located in recesses formed in each end of saidiron core. The inserts are of non-ferrous material since it is necessaryto magnetically insulate the screws from the iron core of the loop. Theloop 23 is also closed at its ends by the insulating discs 36 which areheld in position by the longated screw 31 having a head 38 at one endand a nut 39 at its opposite end. The winding 3| of the loop abovedescribed is ectrically connected to sockets within the junction box I5by the conductors 40 and 4| which extend centrally through the tubularmembers 2| and 22, being suitably insulated and spaced therefrom by thebeads 42. Since a tubular member is secured to each end of the loop aconvenient arrangement is provided as the conductors upon leaving themembers are in the desired position for winding on the iron core. Theend of each conductor within junction box is provided with a plug 43adapted to have interfitting relation with its respective socket. At theother end of the tubular members each conductor extends through a saddlebracket 44 suitably secured to its respective member and to the loop.Certain of the screws 34 pass through the lateral portions of the saddlebracket for securing the bracket to the inserts 35 mounted. on the ironcore 30. Figure 3 is a sectional view illustrating the use of theinsulating beads 42 for centrally positioning the conductors such as thewire lead 40 within its respective tubular member 2|.

The top loop 23 is located directly above the bottom loop 26 and saidloops have a fixed right angular relation. The yokes formed by themembers 2| and 22 and 24 and 25, respectively, support said loops oneabove the other and therefore the yokes are likewise arranged at rightangles. The bottom loop 26 is similar in construction to the top loopand the same is supported by means of saddle brackets at its respectiveends on the tubular members 24 and 25. The coreof the bottom loop 26 isnot shown in Figure 2 but it will be understood that an elongated coreof finely divided iron particles is employed, suitably encased within aninsulating shell or form providing the desired recess for receiving thewindings of the coil 45. Said coil extends for substantially the lengthof the iron core and the same has close association therewith. The coreand coil combination is suitably enclosed within the tubular casing 46which protects the windings from the atmosphere and discs 41 ofinsulating material close the loop at its ends, the said discs beingheld in position by the elon ated screw extending axially of the ironcore and having a head 48 at one end and a nut 49 at its opposite end.

The coil of this bottom loop is electrically connected to sockets withinthe junction box IE by the conductors 50 and 5! which extend centrallythrough the tubular members 24 and 25. In the same manner as describedwith respect to the top loop the said conductors are insulated andspaced from the tubular members by insulating beads. Thus the conductorsare located centrally of their respective tubular member. 7

The end of said conductors within junction box 15 is provided with aplug 52 adapted to have interfitting relation with its respectivesocket. At the opposite end each conductor extends through a saddlebracket 53 and through the insulatin casing 46 of the bottom loop,whereupon the conductor is properly positioned for electricallyconnecting with the ends of the coil 45. The saddle brackets 53 aresimilar in construction and they are employed in a similar manner to thesaid brackets. Each saddle bracket is suitably fixed to the upper end ofits particular tubular member and each bracket performs the function ofsecuring the loop to its tubular member and of also providing a passagefor the conductor or lead to the winding of its particular loop. Thesaddle brackets 53 like brackets 44 are secured by means of screws 34 tometal inserts which are mounted on the iron core of its loop.

In direction finding loops the direction of the transmitter is indicatedby a zero signal when the loop axis points toward the transmitter. It isdesired that only the electromagnetic component of the radio wave act onthe loop and to accomplish this the electrostatic component issuppressed by an electrostatic shield which substantially encases eachloop. Referring to Figures 1 and 2, it will be seen that each loopantenna is covered by special cloth into which metal wires are woven inone direction. This cloth provides the wires 55 which extend around thecylindrical exterior except for a gap at the top of each loop for thepurpose of forming an open circuit for said wires. However, all thewires are electrically connected in the vicinity of the lower portion ofthe casing and the same is grounded at 56 for the top loop and at 5'!for the bottom loop. The insulating discs closing the end of each loopare also covered with cloth providing the vertically disposed wires 58.These wires are also electrically connected at their lower ends and theconnection is suitably ground at 59 for the top loop 23 and 60 for thebottom loop 28.

In actual operation of the loop arrangement herein disclosed the socketsin the junction box l5 are electrically connected to a goniometer by anyconventional means such as a cable, or wires from the sockets may extendindividually through the standards supporting the junction box. Afeature of the invention resides in the provision of tubular members forsupporting the loops one above the other and in right angle relation. Itwill be understood that short leads are desired in a loop antenna andproper shielding especially of the leads to the top loop are a necessaryrequirement for efiicient operation.

The leads in the present structure have a length which is a minimumsince the tubular members are fixed to each loop at its ends where theleads can directly connect with the coil windings. Surplus length asregards the leads is thus eliminated and by means of the beads 42 eachlead is centrally located and insulated from its tubular member. Eachtubular member is also magnetically insulated from the iron core and itsloop since the screws 34 in securing the saddle brackets in place havethreaded connection with non-ferrous inserts 35.

Electric shielding is secured by locating the leads to the loops withinsaid tubular members which for purposes of the present invention aremade of non-ferrous material, preferably brass. The junction box shouldalso be constructed of non-ferrous material in order to complete theelectric shielding. As a result the fields generated by said leads 4!],4 l, for example, included in the electric circuit of the top loop, arenot radiated through the metal barrier and external electromagnetic andelectrostatic fields are prevented from reaching the enclosedconductors. It is particularly important that the leads 40 and 4! beproperly shielded since the currents flowing in these conductors couldotherwise set up electrical influences which would seriously interferewith reception by the bottom loop. It is also important to note that themembers 2| and 22 are located in spaced relation on the respective sidesof the bottom loop. The spacing naturally results by reason of the factthat the loops have a length which is greater than their diameter andthe location of the members at the sides of the bottom loop resents theleast interference to the received radio waves.

What is claimed is:

1. In a loop antenna system, a top loop and a bottom loop each includinga winding having close association with a cylindrical iron core andextending from end to end thereof, supporting means for fixedly mountingthe loops in right angle relation with their magnetic axes horizontal,said supporting means including a pair of upwardly projecting tubularmembers secured to each loop adjacent the respective ends thereof and inclose proximity to the respective ends of the winding on the loop, thetubular members for the top loop extending past the bottom loop on therespective sides and being spaced some distance therefrom, and leadsextendin through said members for electrically connecting with thewindings, said tubular members comprising nonferrous metal whereby theleads are electrically the tubular members of each yoke to its loop,said fastening means being magnetically insulated from the iron core ofits loop, and leads from said junction box extending through the tubularmembers for electrically connecting with the windings, said junction boxand tubular members comprising non-ferrous metal whereby the leads areelectrically shielded.

3. In a loop antenna system, a top loop and a bottom loop each includinga cylindrical iron core having a winding extending from end to end,supporting means for fixedly mounting the loops one above the other inright angle relation with their magnetic axes horizontal, saidsupporting means including a junction box, tubular members projectingupwardly from said box, and a saddle bracket secured to the upperextremity of each member, said members being arranged in pairs toprovide yokes with the saddle brackets of each yoke having securement toits respective loop at the ends thereof, one yoke supporting the bottomloop and the other yoke supporting the top loop, leads from saidjunction box extending through said tubular members and through saidsaddle brackets for electrically connecting with the windings wherebysaid leads have a minimum length, and said junction box and tubularmembers comprising non-ferrous metal for electrically shielding saidleads.

4. In a loop antenna system, a top loop and a bottom loop each includinga cylindrical iron core having a winding extending from end to end,supporting means for fixedly mounting the loops in right angle relationwith one loop directly over the other, said supporting means comprisingtubular members arranged in pairs to provide yokes with the upperextremity of the members of each yoke having securement to itsrespective loop adjacent the ends thereof, leads for the winding of eachloop whereby the same may be connected in an electric circuit, saidleads extending through the tubular members whereby they have minimumlength and are properly positioned for connection with the respectiveends of the loop windings, and said tubular members comprisingnonferrous metal for electrically shielding said leads.

FRED E. JOHNSTON.

